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https://github.com/myrho/elm-round
Round floats (mathematically/commercially) to a given number of decimal places
https://github.com/myrho/elm-round
Last synced: 5 days ago
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Round floats (mathematically/commercially) to a given number of decimal places
- Host: GitHub
- URL: https://github.com/myrho/elm-round
- Owner: myrho
- License: bsd-3-clause
- Created: 2016-10-31T15:52:12.000Z (about 8 years ago)
- Default Branch: master
- Last Pushed: 2022-11-18T11:06:45.000Z (almost 2 years ago)
- Last Synced: 2024-05-21T01:07:07.008Z (6 months ago)
- Language: Elm
- Homepage: http://package.elm-lang.org/packages/myrho/elm-round/latest
- Size: 48.8 KB
- Stars: 46
- Watchers: 2
- Forks: 4
- Open Issues: 3
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
- awesome-ccamel - myrho/elm-round - Round floats (mathematically/commercially) to a given number of decimal places (Elm)
README
# elm-round
This library converts a `Float` to a `String` with ultimate
control how many digits after the decimal point are shown and how the remaining
digits are rounded. It rounds, floors and ceils the "common" way (ie. [half
up](https://en.wikipedia.org/wiki/Rounding#Round_half_up)) or the "commercial"
way (ie. [half away from
zero](https://en.wikipedia.org/wiki/Rounding#Round_half_away_from_zero)).
Example:
```elm
x = 3.141592653589793
round 2 x -- "3.14"
round 4 x -- "3.1416"
ceiling 2 x -- "3.15"
floor 4 x -- "3.1415"
```
The given number of digits after decimal point can also be negative.
```elm
x = 213.14
round -2 x -- "200"
round -1 x -- "210"
ceiling -2 x -- "300"
floor -3 x -- "0"
```
[Commercial
rounding](https://en.wikipedia.org/wiki/Rounding#Round_half_away_from_zero)
means that negative and positive numbers are treated symmetrically. It affects
numbers whose last digit equals 5. For example:
```elm
x = -0.5
round 0 x -- "0"
roundCom 0 x -- "-1"
floor 0 x -- "-1"
floorCom 0 x -- "0"
ceiling 0 x -- "0"
ceilingCom 0 x -- "-1"
```
Have a look at the tests for more examples!
Why couldn't you just do `x * 1000 |> round |> toFloat |> (flip (/)) 1000` in
order to round to 3 digits after comma? Due to floating point
arithmetic it might happen that it results into someting like
`3.1416000000001`,
although we just wanted `3.1416`.
Under the hood this library converts the `Float` into a `String` and rounds it
char-wise. Hence it's safe from floating point arithmetic weirdness.
## Installation
From the root of your [Elm](http://elm-lang.org) project run
elm install myrho/elm-round
Import it in your Elm modules:
```elm
import Round
```
## Releases
| Version | Notes |
| ------- | ----- |
| 1.0.4 | Upgrade to Elm 0.19 |
| 1.0.3 | Fix issues with number in scientific notation, complete rewrite. |
| 1.0.2 | Given number of digits after decimal point can be negative. |
| 1.0.1 | Upgrade to Elm 0.18 |
| 1.0.0 | First official release, streamlined API and tests, docs added |